Number of integral points in a certain sequence of closed quadrilaterals.

Terms

a(0) =3a(1) =5a(2) =8a(3) =12a(4) =17a(5) =23a(6) =30a(7) =37a(8) =45a(9) =54a(10) =64a(11) =75a(12) =87a(13) =99a(14) =112a(15) =126a(16) =141a(17) =157a(18) =174a(19) =191a(20) =209a(21) =228a(22) =248a(23) =269a(24) =291a(25) =313a(26) =336a(27) =360a(28) =385a(29) =411